Tutu was to be a panelist on BBC World Debate alongside Britain's former prime minister Blair, a panel discussion moderated by Zeinab Badawi of BBC World News.

The BBC on Wednesday confirmed that Tutu had withdrawn from the television programme, which was to be filmed in Johannesburg on Wednesday.

"We can confirm that he will not be taking part in this debate – which … is part of the Why Poverty? season to be aired in the autumn on the BBC," said Paul Rasmussen of the BBC Global News Press Office.

Also scheduled to appear in the discussion are analyst Moeletsi Mbeki of the South African Institute of International Affairs and social justice activist Vandana Shiva. An invitation sent out last week to organisations wanting to attend the recording said "the debate will ask why so many people remain poor despite rapid economic growth in the developing world and rising incomes globally, and what should be done".

Rasmussen said that because of the format of the programme, which takes the form of a broad discussion, there will be no direct replacement for Tutu.

The Nobel Peace Prize winner has said Blair's support of the United States's military invasion of Iraq in 2003 was "morally indefensible". The invasion was predicated on unproven allegations that Iraq had weapons of mass destruction.

Tutu's office released a statement earlier this week saying: "The Discovery Invest Leadership Summit has leadership as its theme. Morality and leadership are indivisible. In this context, it would be inappropriate and untenable for the archbishop to share a platform with Blair."

Sports scientist Professor Tim Noakes was due to replace Archbishop Emeritus Desmond Tutu as a speaker at the summit.

Discovery spokesperson Duke Malan said on Wednesday Noakes was approached shortly after Tutu announced that he would not attend.

"When the news came out that the archbishop would not be attending, we spoke to Prof Noakes and he agreed. He is very excited as this is a very big platform," he said. "We had spoken to Prof Noakes about the summit a while back, but there wasn't enough space on the programme."

Other guests at the event include chess grandmaster Garry Kasparov and Finance Minister Pravin Gordhan.

It added that Blair and Tutu have always disagreed about removing Saddam by force and that this was part of a healthy democracy.

In response to questions over the morality of supporting the war, Blair’s office said: "As for the morality of that decision we have recently had both the memorial of the Halabja massacre where thousands of people were murdered in one day by Saddam's use of chemical weapons; and that of the Iran-Iraq war where casualties numbered up to a million including many killed by chemical weapons.

"So these decisions are never easy morally or politically."

There has been growing anger over the invitation extended to Blair from local groups who had opposed the Iraq war. The South African Muslim Network has said that it was considering holding protests outside the summit venue, sit-ins and legal action against Blair.

On Wednesday the South African Press Association reported that the Society for the Protection of our Constitution (Spoc) had filed a complaint with the South African Police Service and that a "crimes against the state" docket had been opened. A case number was issued and the matter will now go to the national director of public prosecutions for consideration.

A war crimes tribunal in Kuala Lumpur last year found Blair and former US president George W Bush guilty in absentia of crimes against humanity.

There has been growing speculation on whether a member of the South African public will attempt to effect a citizens arrest of Blair while he is in the country, in line with a request made by the website www.arrestblair.org. The site offers a cash bounty to anyone who attempts a "peaceful citizen's arrest" of Blair for crimes against peace.

According to the criteria laid down by the site, this involves gently laying a hand on Blair and saying: “Mr Blair, this is a citizens’ arrest for a crime against peace, namely your decision to launch an unprovoked war against Iraq. I am inviting you to accompany me to a police station to answer the charge.” The arrest must reported in at least one mainstream media outlet to qualify for the reward.

"Your attempts to arrest Mr Blair will, at this stage, be largely symbolic, but they will have great political resonance," say the site authors.

Four people have successfully carried out such citizen’s arrests, each netting in between £2 000 and £3 000 as bounty. Three of them donated their rewards to humanitiarian efforts in Palestine and Iraq. – additional reporting by Sapa